PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.NEW Womens SODA SANDY Black Slip On Loafers l Dress Walking Shoe SZ 8.5Old Beijing Cloth Embroidered Shoes Cross Stitch redHalogen Size 8.5W Navy Blue Suede Leather 1" Heel Slides Close ToedDuck Head Size 6 1/2M Judy Shoes - MahoganyWomen's Sperry Top-Sider Navy Blue Rubber Boat Shoes 7 M , Sanuk Maisie Women's Shoes Natural Stripes 9 , Sperry Top-Sider Bluefish 2 Eye Womens Linen/Oat Boat ShoesEurostep Barbara mary jane wedges brown leather 6.5 NEW , Havana Joe Brown Oxfords Womens Size 37Mens New Slip On Patent Shiny tassel Driving Smart Casual Loafers Leather ShoesBite Y-Zone Women's White Golf Shoes Size 8 New With Tags Style: 7502A (b24) , Women's Air Max 1 Essential Running Shoes size 8 womenEarth Zag Womens Velour Fashion Sneaker Shoe Sz 7B BlackNike Women's Free 5.0 women's 9.5 blue print , SAUCONY GUIDE 3 RUNNING SHOES - MULTI COLOR ( SIZE 6 ) WOMEN`SNike 407847-003 Womens Dual Fusion ST Running Shoes Sneakers Size 6 Gray PinkNike Women’s Reax Run 6 Grey Silver Pink Running Shoes Size US 6.5 FAST FREE SHI , Splendid Womens Delta Shoe- Pick SZ/Color. , Converse Chuck Taylor All Star Ox Rose Quartz White Womens Canvas TrainersNike Women's Sneakerboot Roshe Two Hi Flyknit College Navy Blue Sz 8 861708-400KEEN Women's Water Resistant Green Leather Grip Work Shoe US 9Converse Chuck Taylor All Star Shoreline Slip Women's Shoes Mica Green 561751F , Sam Edelman MARGOT Women US 7 Black Shimmering Sneakers High Tops , adidas SL Loop Racer - Green - Womens , New Women's Sperry STS96994 Seacost Slip On Sneakers -Tan Size 7 (I5) , Vans SK8 HI SLIM Neon Leather /Neon Blue Women's Shoes 7Wink by Sugar Hankies Black Canvas Wedge Heel Sneakers Shoes 7H , Adidas Performance X 17.2 FG Rare Women Size 6.5 Soccer Cleats Black Red BA8563 , New Balance WOMENS WW496WB3 White and Blue Walking Shoe Atheletic Size 5BConverse Ctas Brea Hi Brake 551584C
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."